Electric gauge



Y Feb. 24, 1942. V Y `R; MBGANgr-:ITAL Y. 2,274,557 'Y ELEGTRICGAUGEFiled July 1Q, 1940 :ev Sheets-sheet 1 Fig. 1'.

INVENTORS i :Wheels of the motor vehicle, and

Patented Feb. 24, 1942 ELECTRIC GAUGE Raymond Morgan, Philadelphia, andRembrandt D. Summers, Rockledge, Pa.-y

Appiication July,V 1o, 1`94o,.seria1 344,816

largely upon rdenserCg.

A principal object of this inventionv is to provide'a relatively simpleand practical electric de- 3j vice for gauging-'conditions whichare'subject to variations or fluctuations, said device being operativeto afforda. gaugel readingl at, a point orpoints remote-to immediatearea within which the said conditions exist. Y 'Y A'rnore specific`object of rtheiinvention is to provide a'simple and practical devicefor gauging the air pressures inthe-tires of a motor vehicle, saiddevicevbeing operative from the interior of the vehicle and avoiding thenecessityfor use of the conventional type of pressure gauge.

Another object of theinvention is to provide an kelectrically-operateddevice of the character described which avoids theV necessity forarwired connection betweenthe wheels of thev vehicle and the indicator,which as set forth may be located in the interiorof the vehicle; body. f

i A preferred embodiment of the invention is illustrated Vin the'attached' drawingsi in which:

` Figure lisa diagrammatic view'illustrating the essential elements oftile electrical circuits embraced by the" device; y Fig. 2 is adiagrammatic lview illustrating one circuit or Fig. 3 is a VdiagrammaticView in sectional fper ythe setting of 4the variable con- Circuit 3comprises a coil L3 and a gaseous dischargetube I1, and the coil L3 isso relatively arranged with respect to the coils L1 and Lz ofthecircuits I andA 2 that the saidcoil L3 is more closelycoupledinductively to the coil Lz than to the coil L1.

tory circuit I.

It will be apparent that the transfer of energy from circuit I tocircuit 2 will depend upon the relative frequency conditions of the twocircuits,"

themaximum energy transfer taking place -when the frequency of theoscillations in circuit I core responds substantially to the resonantfrequency of circuit 2, or in other words when circuit 2 is tunedto'resonate at the frequency of the oscilla- Therefore, the tube I; maybe caused to operate in dependence upon the relative frequencyconditions of thercircuits I and 2. By suitable design, the necessaryoperating voltageA for tube I; appearing across La maybe made to appearwhen the energy transfer corresponds form of mechanical connectionbetween one of l n f the tires and the electrical system;

spective illustrating the relation of thevarious elements of theelectrical system and one Fig.A 4 is a diagrammatic vievv illustrating amodification within the scope `of the invention.

As illustrated in Fig. A1, the' device comprises an electrical4'systemcomprising three separat-e vcircuits dL-iignated'respctively bythe reference numerals I, 2 and 3'. The' circuit I comprises a coill Li,a'variablecondenser C1, anda spark "gap, Y Swhich may suitably beconstituted by one or morefof 'thffspark plugs of the internalcombustionengin of the motor vehie1e-Theeirc1ut I,

therefore;` constitutes an oscillatoryiciircuit in which electricoscillations are produced by discharges across the gap-S, and thefrequency of the oscillations .ink this circuit'can .be changed byvarying fthe capacitance of the variable convCircuit 2 comprises acoilrLz and la variable condenser Cz. Y The coilsv L1 and Lz'- of thecircuits -I' and-2 respectively are relatively varranged so i that i theformer is` yinductively coupled `to the latter. "Ihezcircuitv 2,therefore, constitutes also an oscillatory circuit, and the naturalfrequency of the electric oscillationsof this circuit depends of the.

`tuned relative to oneanOther,

to some particular frequency relation of the circuits other than a tunedcondition of the two circuits, or ,the design may be such that thenecessal'y'voltage to operate tubek I3 will appear across Y LaAionly'when the two circuits are substantially Preferably the latter designshould' be employed. The design of the system will, of course, depend onthe nature of tube I3, the number of vturns in the coils, the degree ofcoupling, etc.

In accordance with our invention, the coil L2 of the circuit2 is mountedcoaxially upon one of A the Wheels of the motor vehicle, as illustrateddiagrammatically in Fig. 3, wherein the reference numeral 4 indicatesthe rim offthe wheel, 5 the Ytire casing, and 6 the inner tube. Y TheVariable condenser Czfalso mountedupon the Wheel, is mechanicallyconnected with the inner tube 6 so that the setting of the condenser,and hence the .naturaly frequencyV ofl the electric oscillations in 1the ,circuit 2,.is controlled bythe amount of air pressure in4 the tire.rlhis mechanical connection is best illustrated in Fig. 2, and comprisesa plate 1 which bearsagainsttheinner tube 6 and which. is supported onVaplunger 8 which passes slidably through an aperture in the rim 4 andseats at 9 upon the end of a rod I0. The rod I0 Vis threaded forreception of a nut lfI and alock nut I2, the first .ofV thesenutsconstituting a seat for a coiledf` spring 4I3 which embraces the rodI0 Iand which seatsat itsopposite end against aflxed stop vI4 which isrigidly fixed to the wheel structure. The spring I3 vthereby functionstoexert body of the condenser.

' hicle, preferably at the dashboard.

- `The frequency f1 of electric oscillations in the a longitudinalpressure upon the rod I0, and through the plunger 8 exerts pressureforcing theplate 'I against the wall of the inner tube G. The amount ofthis pressure may be varied. by adjustment of vthe nut I I and lock nutI2.

Carried by the shaft of the variable condenser C2 is a toothed wheel I5which engages a rack I6 on the rod i0, and the rod I0 is held inoperative engagement with the toothed wheel I5 by the stop I4 through'anaperture in which the rod I extends and by a guide I8 on the fixed Aspring I'I attached to the body of the condenser and to the sprocket I5Vor to the condenser shaft serves to take up lostmotion between the rackI6 and the toothed wheel I5. By means of the aforedescribed mechanicalconnection, it will be apparent that the setting of the condenser Cz isdetermined directly by the extent to which the inner tube 6 is inated,or in other words, by the amount of Y operation within' the body of themotor vehicle,

such, for example, as on the dashboard, and'lthe Vdial of this condenseris preferably calibrated in numbers to correspond to pounds per squareinch of air pressurein the tire tube 6. f

The coil La is also mounted on the chassis of the motor vehicle and, aspreviously set forth, in

. such position as to be more closely coupled inductively to the coil L2than to the coil L1. The tube I3 of the circuit 3 may be mounted at anysuitable point within the body of the motor vecircuit I, which isdetermined by Ythe manual setting of condenser C1, will beVapproximately thejfrequency given by the relation LUM/nc,

' Similarly,`the natural frequency f2 of the circuit 2, which isdetermined by the above-mentioned adjustment of condenser Cz will beapproximately the frequency Vgiven by -the relation l 'f2-avm The coilsL1 and L2 and condensers C1 and C2 are so designed that the value of thefrequency vtire tube 6.

yIt will be apparent that in the aforedescribed Ydevice, the' circuit Iconstitutes in effect a source of electricV oscillations whose frequencymay be manually controlled. In the'specic embodiment ofthe vinventiondescribed, this` circuit is energized, as a matter of convenience, fromthe ignition Vsystem of amotor'vehicle, but obviously the circuit may beenergized from any suitable source without affecting the operation ofthe device as a whole.- Th circuit 21 constitutes in effect a transfermeans which Yreceives electric Y energy from the circuit VI andtransfers this energy to the circuit 3. andlthe resonant frequency ofthe circuit 2, through the variable condenser C2, is directlycontrolled, in the present instance, by the variable pressure conditionin the inner tube of a vehicle tire. I'he circuit 3 constitutes anindicating means which is operative only when the frequencycharacteristics of the circuits I and 2 have a predetermined relation.

In the particular embodiment described, the resonant frequency of thecircuit I is selectively controllable through the variable condenser C1,but it will be apparent that for certain purposes. the resonantfrequency of this circuit may be a definitely established one, in whichcase the indicating means represented by the circuit 3 would operatewhen and only when the resonant frequency of the circuit 2, through themedium of theV variable condenser C2, is brought into the aforesaidpredetermined relationship with the established resonant frequency ofthe circuit I. Under these latter circumstances, operation of -theindicating means would indicate a certain specific condition of pressurein the tire tube. It is apparent also that substantially the same resultmight be obtained by designing the circuits land 2 so that they have avpredetermined frequency relation, i. e., using xed condensers, and byarranging in circuit 2 a normally-open switch arranged to be closed whenthe tire tube reaches a given condition of deflation. Neither of the twolast described modifications is considered practical in the particularapplicationrof the device herein described, namely, as a motor vehicletire gauge, but it is believed obvious that such modications mightconstitute a desirable form of the device for gauging other variableconditions, and primarily as a means for signalling that acertaincritical condition has been attained or is being maintained.

It will be understood that in the application of the device to a motorvehicle tire gauge, there will, preferably, be one of the aforedescribedelectrical systems associated with each of the vehicle wheels or tires,and that the said systems will then operate independently to gauge thepressures in the respective tires vwith which they are individuallyassociated. The circuit I is provided with a normally open switch I9,which when closed actuates the device as described above.

The modication of the device shown in Fig. 4 is adapted primarily forgauging the temperature of a tire. In this case, the resonant frequencyof the circuit 2 is varied through the medium of a plurality of fixedcondensers Ca, C4, Cs and Cs, and a thermometer 20 which is arranged inthermal relation with the tire or tire tube. The circuit includes themercury or other electrically conductive medium which constitutes theactive element of the thermometer, and as the temperature increases, thecondensers are successively connected in the circuit by the risingcolumnv in the thermometer in obvious manner. The approximatetemperature of the tire may be determined by manipulation of thecondenser C1 of the circuit l, the dial of which in this case iscalibrated in terms of degrees of temperature.

A plurality of fixed condensers, as described above, may also besubstituted for the variable condenser C2 in the pressure gaugeembodiment vpreviously described. In such case, the rack and piniondevice shown in Fig. 2 would be replaced by a sliding electric contactwhich would vary vthe number of the fixed condensers connected in thecircuit in accordance with the variations of pressure in the tire.Similarly, a plurality of fixed condcnsers, with suitable means forvarying tnenumber ot' the condensers connected in the circuit, might beused instead of the Variable condenser Ci of circuit I. Fixed condenserswould have the advantages over the variable condensers of being moreeasily insulated at the relatively liigh voltages used; of Vrequiringfewer,

simpler and lighter control parts; and of being the resonant frequencyof the said tuned circuit` in accordance with variations in the saidcondition in the rotating member.

2. In combination, an internal combustion engine comprising electricalignition means, a ro-l tary driven member, and means for measuring somevariable condition in said member, said means comprising an oscillatingcircuit energized solely from a spark source in said ignition system, awork circuit, a tuned circuit on said rotary member forming a couplingbetween said oscillating and work circuits, said Work circuit havingnegligible direct coupling with the oscillating circuit and therebybeing inoperative except ior the aforesaid coupling through the tuned'circuit on the rotary member, and means lor modifying the resonantfrequency of the said tuned circuit lin accordance with variations insaid condition in the rotary member.

RAYMOND MORGAN. REMBRANDT D. SUMMERS.

